Background: Oncolytic properties had been demonstrated in Mammalian Orthoreovirus (MRV) and Avian Orthorevirus (ARV). Besides MRV and ARV, Pteropine Orthoreovirus (PRV) is also categorized under the genus Orthoreovirus. PRV7S (Sikamat virus) is an orthoreovirus isolated in Malaysia. Present study aims to investigate the oncolytic effects of PRV7S on ranges of nasopharyngeal carcinoma (NPC) cells through apoptosis in comparison to MRV3. Methods: Non-cancerous nasopharyngeal (NCNP) and NPC cells were infected by PRV7S and MRV3. The effects of PRV7S on the proliferation inhibition and apoptotic activity of NPC cells was examined using MTT assay and flow cytometry. Additionally, western blot assay was performed to analyze the expression of RAS and apoptotic protein. Lastly, qPCR assay was performed to demonstrate that PRV7S and MRV3 replicated in infected-NPC and infected-NCNP cells. Results: The proliferation of NPC cells were significantly inhibited after PRV7S infection in a time dependent manner in comparison to infected-NCPC cells. Flow cytometry analysis showed that PRV7S infection was able to induce apoptosis on NPC cells at 48 hpi. Western blot results showed that upon PRV7S infection, N/H/K RAS protein expression was reduced, whereas caspase-3 protein expression increased in NPC cells. qPCR assay showed higher viral load of PRV7S found in infected-NPC compared to infected-NCNP cells. Conclusions: PRV7S inhibits the proliferation and induces apoptosis of NPC cells similar to MRV3. Therefore, PRV7S is a potential oncolytic virus.

Pteropine orthoreovirus (PRV), an emerging bat‐borne virus, has been linked to cases of acute respiratory infections (ARI) in humans. The prevalence, epidemiology and genomic diversity of PRV among ARI of unknown origin were studied. Among 632 urban outpatients tested negative for all known respiratory viruses, 2.2% were PRV‐positive. Patients mainly presented with moderate to severe forms of cough, sore throat and muscle ache, but rarely with fever. Phylogenetic analysis revealed that over 90% of patients infected with the Melaka virus (MelV)‐like PRV, while one patient infected with the Pulau virus previously found only in fruit bats. Human oral keratinocytes and nasopharyngeal epithelial cells were susceptible to clinical isolates of PRV, including the newly isolated MelV‐like 12MYKLU1034. Whole genome sequence of 12MYKLU1034 using Nanopore technique revealed a novel reassortant strain. Evolutionary analysis of the global PRV strains suggests the continuous evolution of PRV through genetic reassortment among PRV strains circulating in human, bats and non‐human primate hosts, creating a spectrum of reassortant lineages with complex evolutionary characteristics. In summary, the role of PRV as a common etiologic agent of ARI is evident. Continuous monitoring of PRV prevalence, pathogenicity and diversity among human and animal hosts is important to trace the emergence of novel reassortants.